CONDUCTIVITY-PEAK BROADENING IN THE QUANTUM HALL REGIME

We argue that hopping conductivity dominated on both sides of sigma(xx ) peaks in low-mobility samples and use a theory of hopping of interac ting electrons to estimate a width DELTAupsilon of the peaks. Explicit expressions for DELTAupsilon as a function of the temperature T, curr ent J, and frequency omega are found. It is shown that DELTAupsilon gr ows with T as (T/T1)kappa, where kappa is the inverse-localization-len gth exponent. The current J is shown to affect the peak width like the effective temperature T(eff) (J) is-proportional-to J1/2 if T(eff) (J ) much greater than T. The broadening of the Ohmic ac-conductivity pea ks with frequency omega is found to be determined by the effective tem perature T(eff) (omega) - homega/k(B)BAR.